Hitherto, a plurality of electrical wires having a terminal are bundled together and are used in the form of a so-called wire harness in a wiring structure of electrical devices including a transportation device such as a motor vehicle or the like and a control device such as an industrial robot or the like. As the constituting material of a conductor for the electrical wire of the wire harness, copper containing materials such as copper, copper alloy and the like superior in electrical conductivity are mainly used.
Recently, accompanied with the rapid development of high performance and high functionality on motor vehicles, various types of electrical devices, control devices and the like to be mounted in the motor vehicles are increasing, which thereby brings about an increasing trend of electrical wires to be used in the mentioned devices. In the meanwhile, in recent years, in order to improve fuel efficiency of a transportation device such as a motor vehicle or the like so as to respond ecologically to the environment, it is strongly desired to make such transportation device lighter in weight.
As a lightweight solution to the electrical wires, it has been considered to use an aluminum electrical wire in which aluminum having a specific weight of about ⅓ of copper is used as the conductor. However, compared to the copper containing materials, pure aluminum is inferior in both impact resistance and flexing characteristics. Therefore, if a pure aluminum electrical wire is applied, for example, in dynamic locations such as a door section where open and close operations are performed, a section around an engine subjected to vibrations and the like, it is possible that the pure aluminum electrical wire may break earlier than expected. Thereby, the application of pure aluminum electrical wires is limited to wires of vehicular accessories in a static location which is substantially immobile after installation or in a low-temperature location having a temperature from room temperature to no more than 50° C.
Meanwhile, Japanese Patent No. 4646998 (PTL 1) has disclosed the fabrication of an aluminum alloy wire which has a high strength and a high electrical conductivity and is superior in impact resistance by performing a softening treatment on the wire after elongation and the application of the aluminum alloy wire having a high strength and a high toughness as the conductor of electrical wires in vehicular wire harness. Since the aluminum alloy wire is superior in impact resistance, it can be used in the dynamic locations mentioned in the above.